1. Field of the Invention
The present invention relates to an ink jet recording head and a method of manufacture therefor. More particularly, the invention relates to a method for manufacturing an ink jet recording head which comprises a fine structure that is formed by use of laser beam.
Also, the present invention relates to a laser processing apparatus for processing grooves or the like by irradiating laser beam onto a workpiece, an ink jet recording head whose grooves are processed by the laser processing apparatus, and an ink jet recording apparatus provided with such an ink jet recording head.
2. Related Background Art
Along with the provision of many nozzles and further reduction of its orifice diameter in order to obtain a high resolution by use of an ink jet recording head which performs printing by discharging ink droplets from the orifices of, for example, tens of μm each, the influence of dust particles intermingled when the head is manufactured or when ink flows in the head has become increasingly greater. Therefore it is necessary to take appropriate measures against such unfavorable influences. For example, there has been proposed a method for forming an ink supply inlet and filter at a time by application of Si anisotropic etching as disclosed in Japanese Patent Laid-Open Application No. 5-208503, and a method for providing a filter structure by use of a filter of a three-dimensional configuration in the ink path as disclosed in Japanese Patent Laid-Open Application No. 5-4348. Also, there is a method known as disclosed in Japanese Patent Laid-Open Application No. 3-180355 wherein a stainless steel mesh filter is provided in the ink path.
However, in accordance with the disclosure of Japanese Patent Laid-Open Application No. 5-208503, for example, the filter unit is obtained by such a patterning as to change its resistance against etching solution by implanting boron ions. This undesirably increases greatly the number of head manufacturing processes. Also, while the filter is provided for the ink supply inlet arranged on the upper part of the ink liquid chamber, no particular measures are taken in the manufacture processes to prevent the dust particles from adhering to the space between the ink liquid chamber and other parts.
Also, in accordance with the disclosure of the Japanese Patent Laid-Open Application No. 5-4348, a filler is to be mixed with resin. This makes it difficult to set the hole diameter of the filter freely. Also, in accordance with the disclosure of the Japanese Patent Laid-Open Application No. 3-180355, the number of manufacture processes needed to make the device are increased because of the steps needed to bury the stainless steel mesh filter in the liquid path.
Further, in recent years, laser oscillators are often used as light source for laser processing equipment. Particularly, attention is given to the ultraviolet pulse laser oscillators as a light source of laser processing at the time of abrasion when patterning is performed on polymer without any development. As laser processing apparatuses or systems for processing polymer by utilizing abrasion, there have been proposed those given below. Such apparatuses (disclosed in Japanese Patent Laid-Open Application No. 4-9291 and Japanese Patent Laid-Open Application No. 4-339585) comprise a laser light source; a given pattern; a masking unit provided with a mask which transmits the laser beam from the laser light source to the workpiece side through this pattern; a projection optical system for projecting the laser beam from the laser light source; and measurement and driving system for measuring the workpiece position and causing the workpiece to move.
A laser processing apparatus of this sort is mainly used for processing the discharge ports of an ink jet recording apparatus (refer to Japanese Patent Laid-Open Application No. 2-121842, Japanese Patent Laid-Open Application No. 2-187346, Japanese Patent Laid-Open Application No. 3-101954, Japanese Patent Laid-Open Application No. 3-101960) or for processing the ink paths of an ink jet recording head (Japanese Patent Laid-Open Application No. 2-121845), and for fine processing of other kinds.
In this respect, the ink jet recording head described above is particularly the one which adopts bubble jet method among those heads using ink jet recording methods. Here, the typical structure and principle of a recording apparatus using the bubble jet method are disclosed in the specifications of U.S. Pat. Nos. 4,723,129 and 4,740,796. These are applicable to either of the so-called on-demand type and the continuous type heads. To describe this method by exemplifying the on-demand type, electrothermal transducing elements are arranged for a sheet or liquid passage (ink path) capable of retaining liquid (ink), and then, these elements are caused to generate thermal energy in response to driving signals, hence creating film boiling on the thermoactive surface of a recording head. In this way, a resultant air bubble is formed in the liquid (ink) path one to one with respect to driving signals described above. With the development and contraction of this air bubble, liquid (ink) is discharged from each of the discharge ports in the form of an ink droplet. Here, as the driving signals thus given, it is preferable to make them pulse signals as disclosed in the specifications of U.S. Pat. Nos. 4,463,359 and 4,345,262. Also, regarding the rate of temperature rise on the aforesaid thermoactive surface, it is desirable to adopt the conditions disclosed in the specification of U.S. Pat. No. 4,313,124 for better performance.
The structure of the ink jet recording head described above is arranged by combining discharge ports (orifices), linear or right-angled liquid paths (ink paths), and electro-thermal transducing elements as disclosed in each of the specifications described above, but beside these, it may be possible to arrange a structure where the thermoactive portion is provided in a curved domain as disclosed in the specifications of U.S. Pat. Nos. 4,558,333 and 4,459,600. Furthermore, the structure of the ink jet recording head described above may be such that a common slit is arranged as the discharge ports of electrothermal transducing elements in a plurality thereof as disclosed in Japanese Patent Laid-Open Application No. 59-138461, for example, or an aperture, which absorbs the pressurized waves of thermal energy, is arranged to face the discharge ports as disclosed in Japanese Patent Laid-Open Application No. 59-138461. In this respect, the ink jet recording heads disclosed in the specifications described above are arranged to secure its length corresponding to a given width by combining a plurality of recording heads, respectively. However, it may be possible to construct a single recording head having a length corresponding to a given width (the maximum width of the recording medium that a recording apparatus may be able to record on).
Also, the ink jet recording heads described above may be of the exchangeable chip type wherein the head can be electrically connected with the main body of an apparatus and is ready to receive ink supply, or can be of the cartridge type which is formed as a recording head itself.
However, when fine grooves and others are processed by use of a laser processing apparatus on a workpiece which constitutes a part of an ink jet recording head, it is impossible to form a groove having a three-dimensional wall in a single operation if the wall faces to be formed are three-dimensional with respect to the direction in which the laser beam is irradiated. In this case, multistage processing must be performed using two or more kinds of masks. As a result, a problem is inevitably encountered in that it takes a considerable time to complete processing of the workpiece. Further, the positions of subsequent processings and so on must be arranged to agree with the position of the first processing exactly, necessitating extremely high precision for the required image processing and the provision of a system enabling the precise stepping of workpiece movement, among some others, in order to execute such precise positioning exactly. These requirements result in making the apparatus itself large and more complicated.
On the other hand, among ink jet recording heads, there are some in which extrusions are formed in the ink paths to provide resistance to the ink flow for the purpose of enhancing the discharging properties of ink by controlling the ink supply force so that it stays more in the discharge port side, and that the ink foaming energy is not allowed to escape to the side opposite to the discharge ports. When the conventional laser processing apparatus is used to process grooves each with extrusions for the formation of the ink paths having such extrusions, productivity is extremely reduced for the reasons described above.